This invention relates to surface treating of plastics and other materials, and in particular to a system for creating a corona between a pair of electrodes with only one of the electrodes being driven by a high frequency electrical corona generator.
As explained in U.S. Pat. No. 4,693,869, the disclosure of which is incorporated herein by reference, many plastics, when molded, will not accept an adhesive, a coating, or inks or printing vehicles unless the surface of the plastic has been chemically and/or physically altered. This patent discloses an electrode arrangement for creating a corona for treating such surfaces to accept adhesives, coatings, inks or other materials applied to the surface. While the corona treating arrangement is particularly useful for treating one side of a plastic, the system cannot treat both sides without the plastic material having been passed beneath the electrode arrangement once, and then being turned over and passed beneath the electrode arrangement again. Obviously, when large quantities of plastics are to be treated on all sides, this repeat process tends to be quite slow.